In the context of the present invention the term “hearing device” refers to hearing aids (alternatively called hearing instruments or hearing prostheses) used to compensate hearing impairments of hard of hearing persons as well as to audio and communication devices used to provide sound signals to persons with normal hearing capability, e.g. in order to improve hearing in harsh acoustic surroundings. Such hearing devices are miniature ear-level devices which are typically employed for extended periods of time and are powered by small batteries such as a zinc air button cell. Zinc air batteries provide a high energy capacity in a small package size. However, they usually need to be replaced quite often, for instance every few days in the case of a hearing aid being used many hours per day by a hearing impaired person. The handling of such tiny batteries when trying to replace a depleted battery of a small hearing aid with a full one is especially challenging and time consuming for elderly people who have lost their manual dexterity and possess reduced vision, as commonly occurs with ageing. Therefore, rechargeable batteries such as for instance a nickel metal hydride (NiMH) or a lithium ion accumulator are increasingly being utilised in hearing devices. However, rechargeable batteries have a lower capacity than zinc air batteries and consequently can power a hearing device for a reduced period of time. Hence, it can happen that a hearing device runs out of power for example when the user is travelling or when he forgot to recharge the battery overnight. These situations are obviously very inconvenient for the user, because he often critically depends on a working hearing device to improve his hearing capability.
Thus there is a need for appropriate means that help a user to ensure that his hearing device has sufficient power whenever it is required.